Self-centering chuck



June 25,1946. G; F. WALD 2,402,714.

SELF-CENTERING CHUCK Filed Sept. 1l, 1945 Fig 1.

Aix.

4. J9 @29a 1gb INVENTOR GEQ/QGEEWMQ,

Patented June 25, 1946 UNITED STATES PATENT OFFICE SELF- CENTERING CHUCK George F. Wald, North Olmsted, Ohio, assigner to The American Steel and Wire Company of New Jersey, a corporation of `New Jersey Application September 1l, 1943, Serial No. 502,005

3 Claims. -1

` In the conditioning of the holes in center of the cylindrical metal pieces such as ywire drawing dies by lapping, grinding, or the like, it is necessary to use a quick acting chuck to hold the pieces as they are rotated. The piece must be held rigid and it must revolve absolutely true with respect to its axis.

I Prior to the present invention, chucks that have been available for this purpose have been of the jaw type that are used on lathes. These chucks are expensive and are dangerous to an operator, for it is very easy for him to be injured if he comes in contact with the fast turning jaws, and consequently, such chucks must be used with caution. Additionally, extreme care must be used to guard against the pieces coming loose and flying out of the chuck while in operation` To overcome these objections there has been devised an improved selfcentering chuck which is easy to construct and which is entirely safe to use. The improved chuck is of a cup type, and will be yunderstood by reference to the accompanying drawing, in which:

Figure 1 is a side elevation of the improved chuck which is shown as being mounted on a suitable rotating means such as an electric motor;

Figure 2 is a longitudinal sectional elevation taken through the chuck along the axis thereof;

Figure 3 is a view similar to Figure 2 but showing a workpiece, such as a wire-drawing die, mounted in the chuck;

Figure 4 is a side elevation of the body of the chuck;

Figure 5 is an end elevation of the body of the chuck looking towards the left as viewed in Figure 4;

Figure 6 is a side elevation of a cup member adapted to t over the body and to lock the workpiece in place; and

Figure 7 is an end elevation of the cup or cup member of Figure 6, looking towards the left as viewed in Figure 6.

Referring more particularly to the drawing, the improved chuck of the present invention includes a cylindrical body or barrel 9 having a bore Il extending axially therethrough for receiving a shaft I3 of a rotating mechanism, such as an electric motor I5, the chuck being releasably locked to the shaft I3 by means of a screw I1, or other suitable means.

The bore I I communicates with a stepped cone or counterbore I 9, which preferably is constructed with a 45 taper, the cone I9 being provided with a step portion 2l which divides or separates the cone into two conical bores or recesses constituting'seats against which the workpiece, such as a wire-drawing die, may be seated and centered with respect to the body portion of the chuck. In Figure 2 a workpiece or die 23 is shown as seated in the inner conical portion of the recess I9a, and in Figure 3 a workpiece 39 of larger diameter than workpiece 23 is seated in the outer conical portion of the recess I9b. By constructing the chuck body in this manner, wherein the seat for the work is in stepped formation, provision is made for chucking various diameter sizes of wire dies without unduly increasing the length of the chuck body.

The body or barrel 9 of the chuck is provided with a square thread 21 of large pitch for the rapid engagement and disengagement of the cup member 35 which is internally threaded, as is indicated at 31 to engage with the threads 217 the square threads of large pitch being provided to assure a snug t or bearing contact between the cup member 35 and the barrel 3 of the chuck and to maintain the cup tight on the barrel during operation.

The cone I9 centers the workpiece automatically, whether it be of smaller diameter than the bottom portion of the cone, as is indicated by the die 23 in Figure 2, or whether the piece is larger in diameter than the bottom portion of the cone, as is indicated by the die 39 in Figure 3.

In operation, the die is placed in the cup 35 which then is threaded onto the barrel 9 until it nts snugly thereon. This may be done prior to placing the barrel 9 on the shaft I3, after which the assembled chuck is secured to the shaft by tightening screw I1 against the shaft or it may be done with the barrel already on the shaft. The 45 taper on the cone automatically centers the die as the cup is screwed onto the barrel 9 and screwed tight. The cup 35 has a hole 4I through its end to permit access to the workpiece, such as to provide entry for a lapping tool for the die.

As the motor I5 has a high speed, for instance rotating the shaft I3 at 1750 R. P. M., it becomes apparent that a very tight fit is required between the barrel member and the shaft, and between the cup 35 and the barrel so as to avoid any danger of accidental displacement of the parts.

The large pitch of the threads 21 and 31 enables the cup 35 with its contained die to be seated and locked very quickly, as only a quarter turn or half turn on the cup is necessary to secure the cup in place. Also, it is obvious from the construction that the die to be tooled may be inserted in any haphazard manner and yet will be centered perfectly automatically in response to the iixing of the cup, thus saving great amounts of time and labor, this being accomplished by virtue of the taper of the cone. This absolutely accurate centering of the die is of extreme importance in order to assure its being tooled to the requisite degree of accuracy. The present construction also obviates any manual adjustment of the dies in the chuck, as is required with a jaw chuck, for example, in order to obtain proper adjustment. With the present device, adjustment of the die for tooling is eiected automatically.

I claim:

1. A self-centering chuck for holding wiredrawing dies during lapping or grinding thereof or performance of other machining operations thereon, which comprises a threaded barrel member having a bore therethrough adapted to mount the said member on rotary driving means, releasable clamping means for clamping the barrel member to the rotary driving means, a complementarily threaded cup-like member adapted t receive a wire-drawing die to be machined and to t over the said barrel member, the threads on the cup-like member being adapted to engage the threads on the barrel member and to produce a tight iit between the barrel member and the cup-like member, the said cup-like member having a plane inner end surface adapted to engage an end of the die, a, self-centering cone in the barrel member for automatically centering the diesresponsively to the cup-like member being drawn up tightly onto the barrel member, thereby forcing the die into engagement with the cone, the said cone being stepped and defining thereby -coaxial but not coextensive frusto-conical surfaces to receive and center a die of any desired diameter, and an opening in the cup-like member in alignment with the centered die for admission of a machining tool into the die.

2. A self-centering chuck for holding wire- 4 Y ldrawing dies during lapping or grinding thereof or performance of other machining operations thereon, which comprises a threaded barrel member having a bore therethrough adapted to mount the said member on rotary driving means, releasable clamping means for clamping the barrel member to the rotary driving means, a complementarily threaded cup-like member adapted to receive a wire-drawing die to be machined, the cup-like member tting over the said barrel member in threaded engagement therewith and forming a cap therefor, the said cup-like member having an inner end surface adapted to engage an end of the die, a self-centering cone in the barrel member for automatically centering the die relative to the cup-like member, the said cone having a slope of substantially 45 degrees, the said cone being stepped and defining thereby coaxial but not coextensive frusto-conical surfaces to receive and center a die of any desired diameter, and an opening in the cup-like member in alignment with the centered die for admission of a machining tool in the die.

3. A self-centering chuck for receiving a cylindrical workpiece, which comprises, in combination, a screw-threaded barrel member, a rustoconical. surface in the barrel member tapering inwardly thereof adapted to receive the Workpiece, andV a cup-like member screw-threaded complementarily to the barrel member and adapted to be brought into a tight fit therewith, the said cup-like member having a plane-surfaced inner face adapted to contact an end surface of the workpiece and to bring the workpiece into 

